Palichnology of the Lower Devonian Wapske Formation, Perth-Andover- Mount Carleton Region, Northwestern New Brunswick, Eastern Canada
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A tlantic G eology 217 Palichnology of the Lower Devonian Wapske Formation, Perth-Andover- Mount Carleton region, northwestern New Brunswick, eastern Canada Yaojun Han* and Ron K. Pickerill Department o f Geology, University o f New Brunswick, Fredericton, New Brunswick E3B 5A3, Canada Date Received December 13, 1994 Date Accepted February 7, 1995 The Lower Devonian Wapske Formation of the Tobique Group in the Perth-Andover-Mount Carleton region of north western New Brunswick forms part of the tectonostratigraphic Tobique Zone. In this region, the formation is 4000 to 9000 m thick and is interpreted as deep-marine turbiditic in origin. Seven sedimentary facies are recognized. These are: conglomerate facies (Facies 1); massive and parallel-laminated sandstone facies (Facies 2); thin- to thick-bedded sandstone with minor mudstone interbeds and/or mud-capped facies (Facies 3); thin-bedded sandstone and mudstone facies (Facies 4); thin-bed- ded, graded, fine-grained sandstone facies (Facies 5); thin-bedded, fine-grained sandstone and silty mudstone facies (Facies 6); and thin- and medium-bedded siltstone and mudstone facies (Facies 7). These facies are grouped into five facies associa tions reflecting a deep-marine fan system consisting of distributary channels, depositional lobes, lobe or fan fringes, and interchannel areas associated with a basin plain. A relatively diverse and well-preserved ichnofauna, consisting of 23 ichnogenera (41 ichnospecies) and three vernacular ichnotaxa, is systematically described, these comprising Arthraria Billings, 1872; Bergaueria Prantl, 1945; Chondrites von Sternberg, 1833; Cochlichnus Hitchcock, 1858; Cosmorhaphe Fuchs, 1895; Cruziana d’Orbigny, 1842; Dendrotichnium Hantzschel, 1975; Didymaulichnus Young, 1972; Helminthoida Schafhautl, 1851; Helminthopsis Heer, 1877; Hormosiroidea Schaffer, 1928; Monomorphichnus Crimes, 1970; Neonereites Seilacher, 1960; Palaeophycus Hall, 1847; Paleodictyon Meneghini in Murchison, 1850; Phycodes Richter, 1850; Protopaleodictyon KsiqJkiewicz, 1970; Protovirgularia M ’Coy, 1850; Rusophycus Hall, 1852; Skolithos Haldeman, 1840; Taenidium Heer, 1877; Uchirites Macsotay, 1967; Umfolozia Savage, 1971; two track forms and indeterminate scratch markings. Their palaeoenvironmental distribution within the se quence correlates well with the interpreted submarine fan complex and compares favourably with other previously docu mented ichnofaunas from deep-marine fans. Collectively, the ichnofauna of the Wapske Formation is characteristic of Seilacher’s (1967) Nereites ichnofacies. La formation de Wapske du Devonien inferieur du groupe de Tobique dans la region de Perth Andover/mont Carleton du nord-ouest du Nouveau-Brunswick fait partie de la zone tectonostratigraphique de Tobique. Dans cette region, la formation a 4 000 a 9 000 m d’epaisseur et elle est interpretee comme une formation d’origine turbiditique abyssale. On reconnatt sept facies sedimentaires, notamment : le conglomerat (facies 1); un facies de gres lamine massif et parallele (facies 2); un facies de gres en couches epaisses ou minces interstratifie de mudstone en quantite mineure ou couronne de boue (facies 3); un facies de mudstone et de gres en couches minces (facies 4); un facies de gres a grains fins, profile, en couches minces (facies 5); un facies de mudstone vaseux et de gres a grains fins, en couches minces (facies 6); et un facies de mudstone et de microgres en couches minces et moyennes. Ces facies sont groupes en cinq associations de facies correspondant a un systeme en eventail abyssal constitue de defluents, de lobes sedimentaires, de franges en lobe ou en eventail et de zones inter-canaux associees a une plaine synclinale. Une ichnofaune relativement diversifiee et bien preservee, constitute de 23 ichnogenres (41 ichnoespeces) et trois ichnotaxa courants, est decrite de fayon systematique. Ceux-ci comprennent 1’Arthraria Billings, 1872; le Bergaueria Prantl, 1945; les Chondrites von Sternberg, 1833; le Cochlichnus Hitchcock, 1858; le Cosmorhaphe Fuchs, 1895; le Cruziana d’Orbigny, 1842; le Dendrotichnium Hantzschel, 1975; le Didymaulichnus Young, 1972; 1’Helminthoida Schafhautl, 1851; 1’Helminthopsis Heer, 1877; VHormosiroidea Schaffer, 1928; Ic Monomorphichnus Crimes, 1970; le Neonereites Seilacher, 1960; le Palaeophycus Hall, 1847; le Palaeodictyon Meneghini dans Murchison, 1850; le Phycodes Richter, 1850; le Protopaleodictyon Ksi^zkiewicz, 1970; le Protovirgularia M’Coy, 1850; le Rusophycus Hall, 1852; le Skolithos Haldeman, 1840; le Taenidium Heer, 1877; 1’ Uchirites Macsotay, 1967; V Umfolozia Savage, 1971; deux formes de pistes et des marques de grattage. Leur repartition paleoenvironnementale a l’interieur de la sequence correspond bien avec le complexe en eventail sous-marin interprets et elle se compare favorablement avec les autres ichnofaunes des eventails abyssaux documentees auparavant. Collectivement, l’ichnofaune de la formation de Wapske est caracteristique de l’ichnofacies Nereites de Seilacher (1967). [Traduit par la redaction] Introduction tectonostratigraphic Tobique Zone (Fig. 1) (St. Peter, 1978a, The study area is located in northwestern New Brunswick, 1979; Pickerill, 1986, 1991; Wilson, 1990). In this area, the eastern Canada, from Perth-Andover to Mount Carleton, a dis Lower Devonian (Lochkovian-Pragian) Wapske Formation of tance of approximately 93 km, and is part of the the Tobique Group, the subject of this contribution, underlies approximately 205 km^ and has been estimated by St. Peter ♦Present address: Department of Geology, University of Alberta, Edmonton, (1978a,b, 1979) to be between 4000 and 9000 m in thickness. Alberta T6G 2E3, Canada Atlantic Geology 30,217-245(1994) 0843-5561/94/030217-29S5.35/0 2 1 8 H an and P ickerill Fig. 1. Generalized tectonostratigraphic map of New Brunswick, eastern Canada, showing location of the study area (modified from Pickerill, 1986; Fyffe and Fricker, 1987; Wilson, 1990). P-A = Perth-Andover, RB = Riley Brook; N = Nictau; MCP = Mount Carleton Park. Surficial exposure, however, is restricted essentially to road below storm wave base in an outer shelf-upper slope deposi sides in the Riley Brook, Nictau, Mount Carleton Provincial tional environment. In this paper we briefly assess the sedi- Park and Perth-Andover districts (Fig. 1). The most common mentology of the Wapske Formation in more detail than in sedimentary lithofacies are grey, greenish grey or green silt- Pickerill (1986, 1991) and, in particular, describe systemati stones interbedded with varying proportions of grey, greenish cally its contained ichnotaxa. grey and brown, fine- to medium-grained sandstones and mud Ichnological research within the adjacent stones or shales. tectonostratigraphic Aroostook-Matapedia Zone has been con Several authors (e.g., St. Peter, 1978b, 1979, 1981, 1982; ducted by Pickerill (1980, 1981,1987) and Pickerill etal. (1987), Skinner, 1982; Irrinki and Crouse, 1986) have proposed a rela but essentially on strata of Late Ordovician and Early Silurian tively shallow marine, quiet water depositional setting for the age. The ichnology of the Lower Devonian Wapske Formation, Wapske Formation, based essentially on the evidence of its con until now, remains unstudied, except for a short ichnotaxonomic tained faunal communities (see also Boucot and Wilson, 1994). commentary by Pickerill (1991) and a series of more detailed However, an alternative scenario was envisaged by Pickerill ichnotaxonomic studies by Han and Pickerill (1994a,b, 1995). (1986, 1991) who, on sedimentological and taphonomic con Most strata of the Tobique Group in the study area lack body siderations, interpreted the formation as having been deposited fossils; however, many beds contain relatively well-preserved A tlantic G eology 219 and abundant ichnofossils that are considered useful for Faunal evidence, as recently reviewed in Boucot and Wilson palaeoenvironmental interpretation, particularly in view of the (1994), suggests an earliest Lochkovian to latest Pragian age fact that such previous interpretations of the sequence are at for the Wapske Formation. considerable variance. The purpose of this contribution is there Seven sedimentary lithofacies have been recognized in the fore to describe the ichnofaunas from this region and to com Wapske Formation in the present study. These lithofacies, indi ment on their interpreted palaeoenvironmental context. vidually differentiated on the basis of lithology, bed thickness, sandstone/mudstone ratios, bed geometry and contacts and in Stratigraphy and sedimentology ternal sedimentary structures, are summarized in Table 2. They are very similar to several of the seven submarine fan facies The Lower Devonian Tobique Group was originally pro first proposed and described by Mutti and Ricci Lucchi (1972) posed to comprise a basal Costigan Mountain Formation and a and subsequently refined by Walker and Mutti (1973) and Ricci conformably overlying Wapske Formation (St. Peter, 1978b) Lucchi (1975a,b). Associations of these sedimentary facies are (Table 1). The constituent lithotypes in these formations are interpreted as representing particular depositional environments similar, although the relative proportions differ, the Costigan present in a deep-water submarine fan system. These lithofacies, Mountain Formation being dominated by volcanic rocks and their associations and depositional subenvironments will be de the Wapske Formation by siliciclastic strata. Initially, St. Peter scribed separately (Han and Pickerill,